When opening a 1.13.2 world ,which had shulker boxes placed down, in the latest snapshot causes the shulker boxes to lose whatever was inside them.
Linked issues
Comments
migrated
MC-140345
Shulker Boxes losing there contents
Resolved
Duplicate
0
migrated
migrated
(Unassigned)
Unconfirmed
Minecraft 18w48b
Retrieved
Isn't because you upgraded your world, it's because you 'reloaded' the world with upgrading. Duplicate of MC-138938.